Embodiments of the inventive subject matter generally relate to the field of satellite receiver systems, and, more particularly, to techniques for reducing the acquisition time in receiving a satellite signal.
Satellite navigation systems, such as the Global Positioning Satellite (GPS) system or the Global Navigation Satellite System (GLONASS), consist of multiple satellites. A satellite receiver may determine its position on earth using radio frequency signals transmitted along a line-of-sight from several of these satellites. Multiple satellites are often employed in order to improve the accuracy of the satellite receiver's position.
The satellite receiver must first acquire the satellite signals. Each satellite transmits a coarse acquisition code (C/A) made up of a long digital pattern referred to as a pseudorandom noise (PRN) code, in the case of GPS satellites, or a PN code, in the case of GLONASS satellites. When a satellite receiver is first turned on, it searches for satellite signals that match known C/A codes. A match of a known C/A and a Doppler frequency with a received satellite signal identifies the transmitting satellite. However, when multiple satellites are utilized and the length of the C/A is long, the dimensions of the search space increases the acquisition time spent in acquiring the signal. Fast signal acquisition plays an important role in achieving reliable satellite communications. With the increase in demand for satellite-based positioning, fast signal acquisition will be a limiting factor for achieving reliable communications and performance.